Technical Field
The present disclosure relates to a motor temperature estimating device having a polyphase motor current sensors.
Background Art
There is known a motor temperature estimating device having current sensors that detect a current flowing in a U-phase coil, a current flowing in a V-phase coil and a current flowing in a W-phase coil of a three-phase motor. An example of motor temperature estimating devices of this kind is disclosed in JP 2003-284375 A, for example.
In the motor temperature estimating device disclosed in JP 2003-284375 A, transformation from three-phase currents (that is, a current flowing in a U-phase coil, a current flowing in a V-phase coil, and a current flowing in a W-phase coil) into two-phase currents (that is, a D-axis current and a Q-axis current) is carried out. Further, a sum of square values of the two-phase currents (that is, a sum of a square value of the D-axis current and a square value of the Q-axis current) is calculated.
Furthermore, in the motor temperature estimating device disclosed in JP 2003-284375 A, at the time of stopping the three-phase motor, a low-pass filter processing arithmetic operation is carried out, which makes a change of the sum of the square values of the two-phase currents rapider (that is, reduces a delay of the change of the sum of the square values of the two-phase currents) more than at the time of rotation of the three-phase motor, and the amounts of temperature rises of the coils of the three-phase motor are calculated. Further, by adding up the amounts of temperature rises of the coils of the three-phase motor, and an ambient temperature (a mass estimation temperature) of the three-phase motor, the estimation temperatures of the coils of the three-phase motor are calculated.
JP 2003-284375 A is a patent document which may be related to the present disclosure.